Net Loss per Share - Schedule of Outstanding Common Equivalent Shares Excluded from Computation of Diluted Net Loss per Share Attributable to Common Stockholders (Details) - shares shares in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding common equivalent shares	16,006	16,508
Stock Options and ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding common equivalent shares	8,846	10,876
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding common equivalent shares	7,160	5,632